OBJECTIVE: To assess clinical and laboratory parameters and serum cytokine levels in 55 neonates who developed early-onset sepsis. METHODS: Clinical parameters associated with early-onset neonatal sepsis were assessed. White blood cell differential and serum C-reactive protein and glucose levels were measured upon diagnosis of sepsis and 48 hours later. IL-1β, IL-10, IL-6, and TNF-α levels were measured in cord blood samples obtained on the day of diagnosis and from samples collected 48 and 96 hours after treatment onset. RESULTS: Among newborns with early-onset sepsis, the length of hospital stay was inversely correlated with birth weight. Clinical parameters varied widely, especially body temperature. Blood glucose changes - particularly hypoglycemia - were common. Leukopenia, usually due to neutropenia, was the most prevalent change in blood cell count. C-reactive protein levels correlated with the immature-to-total neutrophil ratio. Serum TNF-α and IL-10 levels measured early in the course of sepsis were positively correlated with those detected in cord blood. CONCLUSIONS: Clinical and laboratory parameters varied widely among neonates with sepsis in this sample. In neonates who presented with increased cytokine levels at birth, this abnormality persisted throughout the infectious process.